1. Field of the Invention
The present invention provides organic, spin-applied, scratch-resistant coatings for protection of fragile front-side circuitry from damage during backside fabrication and packaging processes.
2. Description of Related Art
Deep reactive ion etching (DRIE) fabrication is utilized in many microelectromechanical fabrication processes. For example, the demand for flexible microelectromechanical systems (MEMS) requiring tall structure designs, as well as the increased density and performance expectations from the integrated circuit (IC) industry, are driving the need to utilize DRIE in creating deep anisotropic etches of silicon for MEMS and semiconductor device applications. However, during the process, the fragile, etch-sensitive circuitry already constructed on the front side of the wafer is susceptible to damage, both physically due to direct contact with the chuck of the etch chamber, and chemically during the etching process.
Typically, a standard photoresist has been used as a DRIE protective coating. Such material, however, is incapable of providing the necessary plasma- or scratch-resistance and is also known to have problems with material outgassing and stress-related issues. In addition, photoresists generally cannot survive the necessary 110° C. operating temperatures of DRIE. Existing technologies have also relied upon a separate aluminum, SiO2, or aluminum oxide etch stop layer in the device design, but such materials cannot be later removed from the device and thus, must be incorporated into the overall device design. They can also affect the underlying layers, causing device yield loss.
Thus, there is a need in the art for protective coatings that provide the required scratch resistance, while also avoiding the drawbacks of existing coatings. Such materials should not contaminate the etch chamber or tool, avoid outgassing during the etch process, have sufficient hardness to resist physical scratching, avoid any tendency to reflow under temperature conditions of the etch process, and be able to sufficiently cover the device circuitry and planarize its topography without any stress on the device features. Such material should be easily removed after the etch process without any damage or negative effects to the circuitry or the substrate itself. Finally, such material should also be suitable to act as an etch stop layer to avoid the need for a separate layer in the device design.